The present invention relates to a method and apparatus for transferring a toner image from a substrate to a receiving element such as a transfer sheet, and is particularly applicable to the transfer of a toner image obtained by an electrophotographic method. More specifically, the present invention is directed to the transfer of a toner image to a receiving element by bringing a substrate carrying said toner image into surface contact with the receiving element, and applying a high frequency vibration thereto, while applying an electric field and/or pressure across the interface.
In the field of electric photography it is often necessary to transfer a toner image developed on one substrate to a transfer sheet. It is well known in the prior art to effect such transfer by employing such methods as electrostatic attraction, mechanical pressing and tacky adhesion. In the electrostatic method, a transfer sheet is brought into contact with a toner substrate and a corona discharge is applied to the rear surface of the transfer sheet to attract the toner thereto. In the mechanical pressing method, a toner substrate is disposed on a transfer sheet and the composite is conveyed through a pair of opposing pressure rollers, whereby the toner particles are caused to adhere to the transfer sheet. The tacky adhesion method is one in which a transfer sheet containing a tacky layer is pressed against the surface of the toner substrate, to transfer the toner image from said substrate to the transfer sheet adhesively.
According to the present invention, an effective method and apparatus has been developed for transferring a toner image from a toner substrate to a transfer sheet, wherein the toner substrate and transfer sheet are brought together, in face to face contact, and a high frequency low amplitude vibration is applied to said substrate and sheet while they are in contact with each other. Any suitable means can be used to bring the toner substrate and transfer sheet into mutual contact, such as for example, a pair of rollers, and the vibration can be of mechanical or electrical origin. In the case where a pair of opposed rollers are used, the vibration can be applied to the rollers at the point where the toner substrate and the transfer sheet are brought into contact with each other, that is, where they pass through the nip of the rollers. The vibration of the rollers is transferred to said substrate and transfer sheet while they are in contact with each other. Simultaneously with the vibratory energy an electrical voltage and/or mechanical pressure is applied across the toner substrate and the transfer sheet while they are in contact with each other, and this operation effects a uniform transfer of the toner image from the toner substrate to the transfer sheet.
It is therefore an object of the present invention to provide a method and apparatus for transferring a toner image from a toner substrate to a receiving element, wherein a vibration is applied to said substrate and element while they are in contact with each other.
Another object of the present invention is to provide a method and apparatus for transferring a toner image from a toner substrate to a transfer sheet wherein, in addition to said vibration, the toner substrate and the transfer sheet are pressed together and/or a voltage is applied thereto.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.